Auxiliary Transmission Fluid Pump Control Circuit Low
The P2798 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit of the auxiliary transmission fluid pump. This pump is typically used in start-stop systems to maintain transmission fluid pressure when the engine is off. A low circuit condition can be caused by a faulty pump, wiring issues, or a defective PCM.
01. Most Common Causes
- Faulty auxiliary transmission fluid pump
- Open or shorted wiring in the pump control circuit
- Corroded or damaged connectors
- Failed PCM or transmission control module
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission may not shift properly
- Delayed engagement when accelerating from stop
- Possible transmission overheating
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the auxiliary pump wiring and connectors for damage or corrosion.
Step 3: Test the pump control circuit voltage with a multimeter at the pump connector.
Step 4: Check the pump resistance and compare to specifications.
Step 5: If wiring and pump are okay, test the PCM output signal.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can lead to transmission damage or failure, especially in stop-and-go traffic.
How much does it cost to fix?▼
Repair costs typically range from $200 to $600, depending on whether the pump or wiring needs replacement and labor rates.